Gauge



July 23, 1946. n- 2,404,751

GAUGE Filed April 27, 1944 Patented July 23, 1946 UNITED STATES PATENT OFFICE,

GAUGE Edwin H. Schmitt, Cincinnati, Ohio 1944-, Serial No. 533,002

Application April 2'7,

2 Claims.

My invention relates generally to gauges and more specifically to a gaugefor determining the diameter-of the internal; bore of a hole particularlywhere the diameter is in small dimensions such as three-sixteenths inch or less In determining the diameter of a bored hole of small dimensions, the only gauges which are available On the market,, depend for their operationon instruments which seat in the bottom of the hole and in which the diameter of the hole is then determined. There are as tar as I am advised, no gauges for determining the diameter of blind holes.

It is not always practical to determine the diameter of a hole by an instrument which has to extend to the bottom of the hole; particularly when the bores to be gauged are of small diameter,

Itv is the object of my inventionto provide a. gauge for determining the internal bore or diameter of a hole which has a guide in operative association with the gauge, which permits manipulation without the instrument extending down to the bottom of the hole.

It is a further object of my invention to provide a simple device which will gauge the internal bore of a hole with great precision and accuracy, but which may be rapidly manipulated so as to be available for inspection work in connection with large scale factory production of small parts.

It is a further object of my invention to provide a gauge for determining the internal bore of a small hole which will be substantially foolproof so that an ordinary factory operative can manipulate the gauge simply and accurately.

The foregoing objects and other objects to which I will refer in the ensuing specification, I accomplish by that certain combination and arrangement of parts of which I have shown a preferred embodiment.

In the drawing:

Figure 1 is a side elevation of the gauge showing approximately the dimensions of one type of such gauge.

Figure 2 is a section in Figure 1.

Figure 3 illustrates an enlarged sectional view showing parts of the gauge inoperation.

Figure 4-. is a bottom plan View of the gauge.

Figure 5 is a detailed sectional view similar to Figure 3 but showing a modified type of gauge tip.

I have shown a casing I, having a visible indicator 2, mounted on a pivot 3, and with the dial through the gauge shown justably mounted'on the tube 2 4, the gradations of which point of the indicator 2" Preferably the indicator will be encased with a. glass front like a watch to prevent the indicator from being injured during use of the 'gauge. Through the casing. i there extends a plunger rod 6, which has a rack portion 1., which contacts a pinion 8'. Througha. chain of gears 9, 1.6;. and H, the spindle of the indicator is rotated, the movement of the plunger rod. 6 being greatly magnified in the corresponding movement of the tip of the indicator 2, so thata veryslight movement of the plunger rod will result in. a readily visible movement of the indicator.

The casing has a threaded tubular portion l2- which is engaged by: an internally threaded-bushing I3. A manual push button I4 mounted. on the rod l5, presses against a spring l6, which causes. movement of. therplungerrod 6 A spring I], as: illustrated in Figure 2;. causes the plunger rod 6 to be brought back to itsori'ginal: starting position at the end of eachgauging measure ment: whereinjthe push button. Hi is depressed.

The casing I has: a tubular extension I8 through which the piunger rod ii extends. The plunger rod, 6 has an i ternally threadedbore I9 into which is screwed a conical shaped tip 20.

Also mounted on the tube 13 is a gauge member having an annular base 2 l, which may be ad- W by means of set screws 22 and trifurcated arms 23, extending down in a sector-like formation, and with the ends of the arms 23 bent inwardly so that the tips 24 approach a common point.

By observing Fig. 2, it will be seen that the conical shaped member 20 has the outer surface of its point as indicated at 25, engaging the inner surfaces of the tips 25 of the gauge element.

Observing Figure 2, it will be noted that as the conical end 25 is depressed, the tips 24 are spread, and when the tips 24 engage the walls of the hole, the diameter of which is being determined, no further downward movement of the conical shaped member .25 is possible. At this position of movement, the movement of the indicator 2 from its starting position will accurately deterare traversed by the mine the diameter of the hole within which the tips 24 have been expanded.

A guide member 26 of tubular shape, has a lower surface 21 and a hole 28 through which the gauge tips 24 extend. The guide member 26 may be mounted on the tube It as by means of set screws 29. In Figure 5 there is shown a modified type of gauge tip 2411 which is somewhat a during the gauging the position which is better adapted for measuring the'diameter of a blind hole.

In Figure 3 there is indicated at 30, a very small bearing which'however, forms an important structural part of a certain type of gauge for an airplane. It is essential during inspection that the bore in the bearing 30 be accurately gauged, because if it is not, the instrument of which it forms a part will not be accurate. The bearing 30 is greatly magnified in the drawing in Fig. 3. As a matter of fact, the entire bearing is so small that it is difiicult to hold it in the hands.

Observing Figure 3, it will be noted that the member 26 to which we have referred, as a guide, but which might also be called a guard or a depth gauge bushing, has its opening 28 sufliciently smaller than the outside diameter of the bearing 30, so that the bearing will not slide up on the gauge tips. By setting the guide on the tube l8, in a desired position by means of the set screws 29, the distance into which the gauge tips, operation, will extend into the bore of the hole being measured, may be accurately determined, or held to tolerances of such dimensions as .0001 inch or the like.

When the gauge tips are in closed position, they form a very small circular formation, which is accurately machined so that not only the diameter but the contour of a small internal bore may be determined.

If, for example, thehole is out of round, one of the tips may be moved farther than the other two, and this movement will show on the gauge by permitting movement of the indicator beyond indicated with a truly round bore.

Thus the device is available for quantity and high speed production gauging work, and the operation is so simple that an ordinary operator can perform this task.

It should be noted that the particular arrangement of the gears and springs and indicating finger form no part of my invention. The parts can be attached to any standard indicator. My invention is primarily directed towards the gauge 4 tip, its adjustable mounting and the adjustable mounting of the depth controlling guide member.

Modifications in the particular construction 11- lustrated and described will readily occur to those skilled in the art without departing from the novel principle involved.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A gauge for determining the diameter of a hole comprising in combination with a casing having a visible indicator for indicating movement of a plunger rod passing through said casing, a plunger rod, means for manually moving the plunger rod, a tubular member through which said rod extends, a conical shaped member mounted at an end of said rod, a gauge member mounted on said tubular member and comprising an annular base having arms extending sector like toward a common point, said arms having gauge tips arranged in position to have their inner surfaces engaged by the point of said conical member, and a guide carried by said tubular member for limiting the depth to which said gauge tips may extend into a hole the diameter of which is being determined.

2. A gauge for determining the diameter of a hole comprising in combination with a casing having a visible indicator for indicating move ment of a plunger rod passing through said cas ing, a plunger rod, means for manually moving the plunger rod, a tubular member through which said rod extends, a. conical shaped member mounted at an end of said rod, a gauge member mounted on said tubular member and comprising an annular base having arms extending sector like toward a common point, said arms hav-' ing gauge tips arranged in position to have their inner surfaces engaged by the point of said conical member, bular member for limiting the depth'to which said gauge tips may extend into a hole the diameter of which is being determined, and means for adjusting the position of said guide on said EDWIN H. SCHMITT.

tubular member.

a guide carried by said tu 

